AN-20, ammonium thiosulfate (and mixtures of these two materials), as well as monocarbamide dihydrogensulfate, can be
used as N sources in a number of
crops, while also providing ancillary weed control. The amount of nitrogen per gallon of
material, the rate at which
it is applied, and the phytotoxicity of the material determines the crops on
which these can be used.
All of these fertilizer materials, when applied at the proper time and manner, have
the added benefit of
ancillary control of many small (less than 3 inches) broadleaf weeds such as
groundsel, pineapple
weed, shepherdspurse, mallow, pigweed, hairy nightshade, chickweed, and many
others. Poor or
no control is obtained on lambsquarters, purslane, henbit, black nightshade,
knotweed, sowthistle, malva goosefoot and grasses.
When any of these N solutions is used as an N source and timed to provide ancillary weed control,
N sidedressings should be reduced by
at least half the N applied with the solutions.
Cautions
When using these nitrogen sources in foliar applications, follow
cautions listed below. Severe crop
injury may occur if cautions are not observed.
General cautions that apply to nitrogen liquid fertilizer formulations
are:
- Apply only after the first true leaf is as tall as the flag
leaf and before the plants are 8 inches tall.
- Do not apply within 4 days of a period of cool, cloudy or rainy
weather, or if free water is present on the leaves.
- Discontinue application if spray droplets do not roll off or
"bead-up" on the crop leaves. This
indicates a deficiency of adequate waxy cuticle, and may be a temporary
condition due to rapid
growth, cloudy or rainy weather, or more seriously, the lack of adaptability
of the variety.
- Do not apply within 4 days after a foliar pesticide has been applied,
or with any wetting agent.
- Use large nozzles to minimize misting and possible injury to the crop
growing point.
AN-20 fertilizer formulation:
This is a manufactured 20-0-0 formulation (containing 20% N) that may be
applied at 50 to 70
gal product/acre as a foliar spray. This formulation weighs 10.55
lb/gal and
contains 2.11 lb N/gal of product and would provide approximately 100 to
140 lb N/acre (but
some N is lost through volatilization). Do not irrigate for 48 hours after
application, but then irrigate to move the fertilizer into the root zone.
Note: This formulation is different from a solution that could be
prepared by dissolving
ammonium nitrate in water. Such a solution would not have the same
concentration or weed-killing effect.
To prevent crop injury, follow the cautions listed above.
Ammonium Thiosulfate:
This is a manufactured 12-0-0-26 formulation (containing 12% N and 26%
sulfur) and weighs 9.33 lb/gal. It may be applied at 50 to 70 gal product/acre
as a foliar spray. This solution contains 1.12 lb N and 2.4 lb S/gal of product and would
provide approximately 55 to 75 lb N/acre (some N may be lost through volatilization).
At the application volume mentioned, about 150 to 168 lb S/acre are also applied. Do not
irrigate for 48 hours after
application, but irrigate then to move the fertilizer into the root zone.
When this treatment is used, subsequent N sidedressings should be
reduced by a portion of the amount of N applied in the treatment.
Note: Mixtures of AN-20 and ammonium thiosulfate (usually 1:1) can
be made which will reduce
the amount of nitrogen applied, provide some sulfur (compared to AN-20 alone, and
reducing the S compared to ammonium thiosulfate alone), and be as
effective as either material alone. Application rates are still held at 50 to 70 gal of the
mixture/acre.
To prevent crop injury, follow the cautions listed above.
Monocarbamide Dihydrogensulfate (monourea sulfuric
acid, 15-0-0-16, N-pHURIC fertilizer):
This product can be used on onions (bulb and green),
shallots, leeks and garlic only, at 10 to 30 gal product/acre as a foliar spray.
It weighs 12.65 lb/gal and contains
1.9 lb N and 2.0 lb S/gal of product. It is most generally used at about 15
to 20 gal/acre providing approximately 28 to 38 lb N/acre (but some N is lost through
volatilization). Apply in sufficient water to get good foliar coverage (approximately 1:1 dilution).
Do not irrigate for 48 hours after application, but irrigate then to move the fertilizer into the
root zone.
CAUTION: This solution is corrosive, and can injure skin and damage
spray equipment. Use proper safety precautions and suitable spray equipment (stainless steel).
To prevent crop injury, follow the cautions listed above, and
FOLLOW ALL LABEL INSTRUCTIONS.
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